Environmental assessment of diets: overview and guidance on indicator choice

High reliance on fortified foods when optimizing diets of adolescents in Sweden for adequate vitamin D intake and climate sustainability

The global food system contributes roughly one-third of global greenhouse gas emissions (GHGEs) making shifts towards more sustainable food consumption an imperative. Such diets also need to factor in nutrient requirements and cultural acceptability. Our aim was to simulate dietary changes for adolescents in Sweden to achieve the recommended intake (RI) for vitamin D while factoring in additional nutrients, cultural acceptability and keeping the diet within planetary boundaries for climate change. A baseline diet was estimated from Sweden's national dietary survey Riksmaten Adolescents 2016-17 (n = 3099, ages 11-18 years), which provided food intake via two 24-hour recalls. Intake data were linked to the Swedish Food Agency's food composition database and GHGE estimates from the Research Institutes of Sweden's (RISE) Food Climate Database. Linear programming was used to optimize the baseline diet to meet the RI for vitamin D (10 µg/day), reduce GHGEs to ≤ 1.7 kg CO2-equivalents/person/day, and minimize dietary changes from baseline to factor in cultural acceptability. A second optimization included 25 additional nutrients requirements. Both optimized diets met their respective requirements reducing GHGEs by 54 % but relied heavily on milk and yoghurt (fortified by law), which provided > 60 % of vitamin D intake. Both diets also required major shifts toward plant-based foods and the second optimization demanded a five-fold greater change in diet from baseline compared to first optimization. Results suggest that adolescents in Sweden can achieve RIs for vitamin D and other nutrients while greatly reducing diet-related GHGEs, though cultural acceptability may be a challenge.

City Residents Play a Pivotal Role in Managing Global Food Security While Improving Human Health and Minimizing Environmental Footprints

BACKGROUND/OBJECTIVES

Improved global data allow for a new understanding of what impact the food we produce, eat and dispose of has on the environment, human health and Nature's resources. The overall goal is to guide decision-makers and individuals by providing in-depth knowledge about the effects of their dietary preferences on human and environmental health.

METHODS

The method is to investigate ways to reduce environmental degradation and to secure healthy food supplies in an urbanizing world, and to quantify the options.

RESULTS

Reviewed articles show that by eating less meat-based food and more plant-based and soilless food, as well as reducing food waste and recycling urban-disposed nutrients as fertilizers, we could reduce agriculture's land requirement by 50% to 70% while still securing a healthy food supply. Less land under cultivation and pasture would reduce global emissions to air and water to a similar extent, and allow Nature to reclaim freed areas in order to catch more carbon and rejuvenate biodiversity. Thus, we could avoid further environmental degradation such as the current clearing of new fields needed under a business-as-usual regime. Presently, some 17 million people die each year due to poor diets, which is more than double the 7 million deaths since the onset of the COVID-19 pandemic. A return to more plant-based diets with unchanged intake of proteins but less calories, sugar, salt and fat combined with less red meat and ultra-processed food would reduce foremost non-communicable diseases by up to 20% and prolong life. The article suggests that the international focus has gradually turned to the food sector's big contribution to climate change, biodiversity loss and harmful chemicals as well as to poor human health. It argues that this century's rapid population growth and urbanization give urban residents a pivotal role in food's impact on agricultural areas, which today cover half of the globe's inhabitable areas. Their food demand, rather than the activities of farmers, fishermen or loggers, will guide remedial measures to be taken by individuals, industry and the public sector. A tool to calculate the potential environmental footprints of individual or societal measures is presented.

CONCLUSIONS

Measures to make the agrifood sector more sustainable are still pending full recognition in international fora such as the UN COP Summits. Smart cities fitted with infrastructures to recycle macro- and micro-nutrients and organic matter have the potential to ameliorate human-induced impacts such as emissions to air and water bodies, crossing planetary boundaries, and polluting extraction of N (nitrogen), P (phosphorus) and K (potassium). Rapid results are within reach since dietary change and the turn-around time of nutrients in food is short compared to decades or centuries for recycled materials in cars or buildings.

Low-carbon diets across diverse dietary patterns: Addressing population heterogeneity under constrained optimization

Mathematical optimization is a useful tool for modeling diets that fulfill requirements for health and environmental sustainability, however, population-based optimization approaches fail to account for underlying dietary diversity in populations. This study proposes a methodological approach to consider diverse dietary intake patterns in mathematical optimization of nutritionally adequate low-carbon diets and investigates the differences between different population groups, along with trade-offs between greenhouse gas emission (GHGE) reduction and the inconvenience of dietary changes required to achieve optimized diets. A k-means clustering analysis was applied to individual dietary intake data from Denmark, which resulted in four clusters with different dietary patterns. This was followed by quadratic programming, wherein the total dietary changes required from the observed diet within each cluster were used as a proxy for consumer inconvenience (i.e., "inconvenience index") and were minimized while fulfilling nutrient constraints and incrementally tightened GHGE constraints. Across clusters, a steep increase of the inconvenience index was observed at GHGE levels below approximately 3 kg CO2e/10 MJ, corresponding to GHGE reductions of 24-36 % in different clusters. In all clusters, the optimized diets with nutritional and GHGE constraints showed common traits of increased content of cereals and starches, eggs, and fish and decreased amounts of beef and lamb, cheese, animal-based fats, and alcoholic beverages, but differences across clusters were also observed, maintaining characteristics of the clusters' baselines. When additional health-based targets for food amounts were applied as constraints, the optimized diets converged towards the same type of diet. The total inconvenience of dietary changes required to fulfill constraints differed between clusters, indicating that specific sub-populations may be more effective targets for dietary transition. The method has potential for future integration of more sustainability aspects and different consumer preferences.

Food choice, activity level, and carbon footprint: exploring potential for sustainable food consumption practices in young adults

This study aims to explore climate consciousness in relation to food consumption in young adults, examining its relationship with physical activity level and gender. A mixed-method approach is utilized, integrating seven-day food records and semi-structured interviews, employing social practice theory in our analytical framework. Our cohort of 47 participants (25 women, 22 men) displays varied diets, from omnivores to vegans. Moderately-active women show the lowest carbon footprint, favoring climate-conscious choices related to lower energy needs and plant-based preferences. Highly-active individuals consume more energy, resulting in a higher carbon footprint. Gender differences are evident, women were inclined to climate-conscious food practices motivated by animal ethics and health concerns. Conversely, men demonstrated a tendency for meat consumption. Participants share an understanding of carbon footprint, reflecting a solid awareness of food-related climate impact but differ in priorities; performance for highly-active, and economy for moderately-active. This highlights a mix of commonalities and distinctions, informing flexible, sustainable food practices. Higher activity levels are linked to greater energy needs and a higher carbon footprint. Moderately-active women show the most climate-conscious food choices, leading to the lowest carbon footprint. Our findings indicate that highly-active individuals and men have significant potential to improve climate-adapted food consumption.